This invention relates generally to thermoplastic packaging films suitable for cook-in packaging and their use. More particularly, this invention relates to cook-in food packages having food contact surface characteristics which promote binding adherence to a contained food product during cook-in.
Many foods during preprocessing are stuffed into a casing and then placed in a heated medium, such as a hot water bath, for cook-in to produce a precooked, encased food product. The term "cook-in" conventionally refers to cooking of a food product while contained in a package. Alternatively, the package may be a heat-shrinkable bag which shrinks tightly about a contained food product upon initial exposure to cook-in conditions.
The term "cook-in package" is intended to refer to packaging material structurally capable of withstanding exposure to cook-in time-temperature conditions while containing a food product. Cook-in time-temperature conditions typically imply a long slow cook, for example by submersion in water at 70.degree.-80.degree. C. for 4-6 hours. Under such conditions, a packaging material properly characterized as cook-in will maintain heat seal integrity and will be delamination resistant.
It is desirable that a cook-in package closely conform to the contained food product to prevent "cook-out", i.e. exudation of fluids from the food product during cooking. By restricting exudation of fluids from a cook-in contained food product, the yield of the precooked food product is increased, since fluid retention tends to increase product weight.
Of general interest is the disclosure of U.S. Pat. No. 3,743,521 issued July 3, 1973 to Rasmussen for "Coated Fibrous Sausage Casing" directed to a fibrous casing having an internal coating of a cationic thermosetting resin to inhibit the accumulation of fat and gelatin between the casing and a contained sausage product.
Of general interest in the disclosure of U.S. Pat. No. 3,784,711 issued Jan. 8, 1974 to Kane for "Surface Treated Cheese Package and Method" directed to a package of cheese overwrapped in polyester film having a corona treated inner surface to promote adhesion to molten cheese.
Of general interest is the disclosure of U.S. Pat. No. 3,355,319 issued Nov. 28, 1967 to Rees for "Self-Supporting Film With A Heat-Sealable Coating of An Ionic Copolymer Of An Olefin And Carboxylic Acid With Metal Ions Distributed Throughout" directed to a thermoplastic film structure having a heat-sealable coating of an ionic copolymer.
Of general interest is the disclosure of U.S. Pat. No. 4,104,404 issued Aug. 1, 1978 to Bieler et al for "Cross-linked Amide/Olefin Polymeric Tubular Film Co-extruded Laminates" directed to irradiatively cross-linked film having polyamide and polyolefin layers joined by an ionomeric adhesive interlayer.